Widia GTD

CNC Thread Mill Programming


Programming the Correct Tool Path

Do not radial infeed the mill. Thread mills generate high radial forces or "side load pressure". This is due to the "V" form ground on the periphery of the tool. If a thread mill has a 1" length of cut, the effective length of cutting edge engagement is approximately 2". This is the standard length of thread on a 3/8" diameter tool. This equates to a 5.33 length to diameter ratio.

Any effort to avoid immediate side loading to the tool will prevent the possibility of tool breakage or chipping. If a radial infeed is performed, the tool has to come to a complete stop before the 360° arc rotation is performed. Generally, a broken or damaged tool will be the result. Widia GTD (formerly Greenfield) highly recommends the use of a small arc into the part following the helix of the thread to be produced, then the 360° arc around the center of the hole, and completing the operation by arcing away from the threads to blend the thread.